21 Savage's 'Nephew' Dies By Suicide After Allegedly Shooting Sister

A 14-year-old boy -- identified as a "nephew" to rapper 21 Savage -- took his own life after allegedly shooting his sister in the neck ... according to the family.

Cops say they arrived at the scene after receiving reports of gunfire Wednesday ... where they found two people shot -- a boy and a girl.

Police say the boy -- Seven Shirley -- was found with a gunshot wound and no signs of life. The girl -- identified by the family as 12-year-old Lyric Shirley -- suffered a gunshot wound to the neck and was taken to the hospital for emergency medical treatment.

Lyric has gone through multiple surgeries this week ... it's unclear when she'll be cleared by doctors to return home.

Seven's grandmother, Sharon Smith -- who raised Seven from the time he was 11 months old -- told the local outlet 11 Alive he took his own life after shooting his sister.

She says, "Just that fast that boy had made the decision to kill himself. He probably sat up there and thought, 'I'm finna go to jail, they're going to ridicule me, everybody is going to be doing this and that and this, and this and that,' and he couldn't take it."

Smith says she does not know how Seven got a gun ... but she hopes the person who sold it to him is brought to justice.

21 Savage -- who 11 Alive reports has been identified as an "uncle" to Seven -- posted about the young man after his death ... sharing a picture of him when he was a young child with the caption, "Remember when you was a baby."

The family released a statement which reads -- in part -- "As our family grieves, we are asking our community to stand with us in another way. Please help us get these guns off our streets. Far too many young lives are being taken by senseless gun violence. We must work together to stop the illegal sale and access of firearms to minors and do everything we can to protect our children."